Abstract: Vacuum packed leek root that has degenerated in bulging bag was used as raw material to separate and screen spoilage microorganism by pure culture method. The main spoilage bacteria were identified by morphological observation,physiological and biochemical test and 16S rRNA gene sequence analysis. The inhibitory effect of preservatives on the main spoilage bacteria was also studied. The results showed that the dominant spoilage bacteria causing vacuum bag expansion and pickled leek root rot were five strains of bacteria,which was identified to be composed of three Bacillus megaterium and two Bacillus toyonensis. Antiseptic and antibacterial experiments showed that the IC₅₀ of sodium benzoate,potassium sorbate,sodium dehydroacetate,EDTA and sodium pyrosulfite against the spoilage bacteria were 5.63~10.11,11.24~31.33,10.07~18.60,20.68~40.70,15.74~36.37 μg/mL,respectively.The bacteriostatic effects were successively as follows:sodium benzoate > sodium dehydroacetate > potassium sorbate > sodium metabisulfite > EDTA.